Heating-system control



March 26, 1929 P F, SHWER 1,707,193

HEATING SYSTEM CONTROL Filed Nov. 16, 1925 4 Sheets-Sheet l IN VEN TOR.

ATTORNEYJ March 26, 1929. P, SH ERS 1,707,193

I HEATING SYSTEM CONTROL Filed Nov. 16, 1925 4 Sheets-Sheet 2 INT 'EJVTOR- .4 TTORNEYS March 26, 1929. p SHIVERS 1,707,193

HEATING SYSTEM CONTROL Filed Nov. 16, 1925 4 Sheets-Sheet 3 I XVEN TOR.

Paul F. 5/1 z'l ezzs,

A TTORXE Y J March 26, 1929. p s v Rs 1,707,193

HEATING SYSTEM CONTROL Filed Nov. 16, 1925 4 Sheets-Sheet 4 1N1 'EX TOR.

Paul 1 'ln'l em A TTORNEYS Patented Mar. 26, 1929.

* UNITED STATES PATENT- OFFICE.

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Application filed November is, 1925. Serial no. cases.

and on in accordance with the dictates of the requirements of the apartment or apartments to be heated. To this credit is one of the objects of my invention to provide controlling means for the oil supply, in turn controlled by thermostatic means arranged in the apartment or apartments to be supplied by heat, which thermostatic means automatically, as occasion demands, cuts oi the supply or" oil-to the burner and automatically admits a supply of oil to the burner and causes the ignition of said oil dependent upon the variations of heat in the apartment.

Another object of my invention is to provide a control means for the'oil supply which upon. failure of ignition of the fuel supply, either initially or durin the operation of the burner will automatically shut oil the supply of oil to the burner to prevent the flooding thereof, this control being adapted for use in cooperation with the compartment therm0stat1c control or independently where said thermostatic controlis not used.

Another object of my invention is to provide' the above type of control in such a construction that the same is practically fool proof, is proof against tam ering and which will be essentially safe un er all'conditions of operation.

For the purpose of illustrating my invention'I have shown certain embodiments thereof in the accompanying drawin s in which Fig. 1 is a schematic view 0 the physical arrangement of the various heating and con-' trol e ements in connection with a heating plant and apartment to be heated;

Fig. 2 is a diagrammatic view of the circuit arrangement of the electrical apparatus embodying my invention; I

Fig. 3 15a diagrammatic view of the circuit arrangement of the control for the control motor embodied in my invention;

Fig. 4 is a side elevation partly in section of the combustion or stack control thermostat;

Fig. 5 is a front elevation thereof with the cover plate removed;

Fig. 6 is a detail sectional view of the drive between the thermostatic element and the switching mechanism;

Fig. 7 is. a perspective view of a control motor which may be used in connection with my invention, and

Fig. 8 is a detail transverse sectional view thereof. Referring to the drawings the a artment l is supplied with heat from a suitailb le source,

as a furnace 2, which is provided with any type of oil burner 3, this oil burner in turn being supplied from the fuel supply 4 by a pump 5 interposed in the supply line 6, which pump is in turn operated by an electric motor '2, preferably of the alternating current type. The operation of this motor l -is in turn controlled by a motor driven switching mechanism 8, the circuitof the motor of which is subject to the control of a thermostat and a combustion thermostat l0 placed in a position to be subjected directly to the influence of the heat of the combustion chamber of the furnace 2. I have lound'by'experience that the most satisfactory position for this thermostat 10 is in thestack or chimney of the furnace or boiler.

In Figs. 4 to 6 Ihave illustrated a combustion controlled thermostat particularly adapted for use in'connection with my system. This thermostat 10 comprises a suitable supporting member 11 by which the same may be supported in position and a casing 12 for the electric switching mechanism. The support 11 is provided with a bushing 13 which projects into a boss 14 in the casing and provides a suitable bearin member for a spindle or shaft 15. This spmdle or shaft is surroundedby a helically coiled ribbon 9 arranged in the apartment to be heated thermostat 16, one end of which is secured I at 17 to the bushing 13 while the other endis secured at 18 to the spindle, whereby as the thermostat expands or contracts under variations in temperature the spindle will be rotated. The front end of the spindle projects into the casing and carries a rockingarm or support'19 for a pair of mercury tube switches 20 and 23, which switches comprise glass tubes'partially filled with mercury and having projecting thereinto a pair of switch contacts, the contacts being arranged at one end so that as the tube is tilted the mercury will flow toward and bridge the contacts to close the circuit or away from the contacts to open the same. The arm 19 is oscillated by the rotation of the spindle through a friction driving connection comprising a clutch member 22 pinned on the shaft to rotate therewlth and provided with axially extending pins 21 which take into openings on a friction mem ber 24 axially slidable on the spindle 15 and urged toward the clutch member 22 by a-coiled spring 25 interposed between the friction member 24 and a stop washer 26 on the end of the shaft. The arm 19 is frictionally gripped between these two clutch members and at its lower end is provided with limiting stops 27 and 28 adapted to abut against a stop member 29 on the casing. By this arrangement as the spindle is rotated, in either direction, under the influence of the thermostat, the switch arm 19 will be rocked in one direction or the other until the stop members 27 or 28 engage the stop 29 at which time the mercury in one of the tubes will be caused to flow in a direction to bridge the contacts the limiting stops 27 and 28 with the stop 29, will not affect the parts of the switch.

However, immediately upon a reversal of rotation of the spindle the rocking arm will immediately commence to move with the spindle until its movement in the opposite direction is again stopped by the limiting stops.

In Figs. 7 and 8 I have illustrated a type of control device very well adapted for use in connection with my system. As noted, this device is completely enclosed in a casing 30 in which all of the parts of the device and switching mechanism are enclosed. The motor proper 46 is adapted to drive through a suitable gear train 32, a pair of rotary switch arms 33 and 34 adapted to co-operate with contacts on insulating blocks 35 and 36. The casing 30 is provided interiorly with a series of compartments for separating the various mechanism. The motor 46 is mounted in a suitable compartment 37 having its shaft projecting through and into a compare ment 38 in which the gear train 32 is mounted. This compartment is closed by a cover plate 39 through which the driving shaft of the motor projects into a compartment 40 formed on the outer face of the cover plate and enclosing the switch arm 33. The switch arm 34 is mounted in a compartment 41 in the motor casing. which compartment also encloses the mounting block for the various terminal connections, this mounting block being provided exteriorly with suitable binding ports 42 to which the various lead wires may be attached.

The motor is of the alternating current re-- pulsion type and operates on a comparatively high voltage circuit and for controlling the starting and stopping of this motor I introduce in the circuit a transformer 43. The primary winding of the transformer is connected with the supply line in series with the stator winding of the motor while the secmanually controlled switch 44 of the two pole type and normally held in one position under the influence of a coiled spring 45.

Referring now to Fig. 2 which diagrammatically illustrates the circuit arrangement of the respective parts and in which, however, I have illustrated the control motor 46 of the simple repulsion type having a suitable field winding 47 and a rotor 48, the brushes 49 of which are adapted to be short-circuited for starting purposes. The rotary switch arms 33 and 34 are always maintained in a definite relation and rotate in unison when operated by the control motor. The switch arm 34 is provided with a plurality of brushes 50, 51,-

and 52. The brush contact 50 is adapted to sweep over and make engagement, during the rotation of the switch arm, with a stationar contact 53 connected by conductor 54 witli one terminal of the switch 23, the opposite terminal of which is connected by conductor 55 with one brush of the rotor 48 of the control motor. This brush of the motor is likewise connected by a conductor 56 with a series of contacts 57 electrically connected together and in turn these contacts are connected by conductor 58 with the thermostatic member 59 of the thermostat 9. At diametrically opposite points and in the path of the brush contact 51 of the movable switch arm 34, which switch arm sweeps over the contacts 57, I interpose a pair of contacts 60 and 61, respectively connected by conductors 62 and 63 with the stationary contacts 64 and 65 of the thermostat 9. In addition to the above contacts on the control switch I provide an inner circular contact 66 adapted to be engaged by the brush 52 and grounded by conductor 67. The second brush of the rotor of the control motor is grounded as at 68.

The fuel supply motor 7 is controlled by the movement of the switch arm 33 which switch arm is provided with four brushes 69, 70, 71 and 72. The brush 69 is adapted to make continuous engagement with a rin contact 73 connected with one terminal of the stator or field winding 47 of the control motor by the conductor 74. The opposite terminal 87 and 75' with one side 76 of theline.

of this winding 47 is connected by conductor for the purpose of igniting the fuel when the system is started. The brush'71 makes contact with an arcuate contact 81 connected by conductor 82 with one stationary contact 83 of the hand switch 44 and across the switch member 84 with stationary contact 85 in turn connected by conductor 86 to one terminal of the fuel supply motor 7, the opposite terminal of which is connected by conducrtlolrl's e fourth brush of the switch arm 33 is adapted to make contact with the circular contact 90 connected by conductors 91 and 92 with the side 93 of the line. This brush 72 isalso adapted, at a predetermined point, to make contact with a contact segment 94 connected by conductor 95 with one terminal of the switch 20, the opposite terminal being connected by conductor 96 and conductor 92 with the side 93 of the line.

In operation, when the parts are in nonoperating' oosition, that is, when no oil is being supplied to the burner, the switch arms 33 and 34 are in the position illustrated in Fig. 2, with the brush 51 resting on contact segment and the brushes 69 and 72 of switch arm 33 resting on contacts 73 and 90. In the position illustrated in the drawings the thermostatic member 59 will be in neutral or in a position to shut off the supply of fuel and, as the combustion chamber is cool, the combustion thermostat 16 will be in position with the circuits closed through the switch member 23 and open through the switch member 26, as illustrated in Fig. 2. In this position the fuel supply motor circuit will be open and the switch control motor circuit will be in closed condition with brush 51 on contact 66. With the parts in this position, if the compartment temperature falls sufiqcienb ly to require more heat the thermostat 59 will becaused to move to the left and into engagement with contact 64. Initial starting circuit for the control motor will then be established from one pole of the rotor 48 by conductor v arrows.

56, contact 57., conductor 58, thermostatic element 59, contact 64, conductor 62, contact segment 60, brush 51 across the switch arm 34 to brush 52 and contact segment 66, and thence by conductor 67 to ground, thereby short-circuiting, through ground and conductor 68, the brushes of the repulsion motor 46 and starting the motor, which rotates the switch arms 34 and33 from the position illustratedin Fig. 2 and in the direction of the The brush 51 quickly moves off the short contact segment 60 and onto the contact segment 57 thereby establishing a maintaining short-circuit for the brushes of the rotor 48 of the control motor 46, from conductor 56, contact segment 57, brushes 51 and '52, contact segment 66, conductor 67 to. round. At the same time the stator circuit of t 1e control motor is established from line 93 by conductors 92 and 91, contact se ment 90, brushes 72 and 69, contact segment 3, conductor 74, stator winding 47 and by conductor '7 5 to line 76.

By the time'the maintaining circuit has been closed through the control motor the switch arm 33 will have been rotated a suflicient distance for the brush to close the circuit through the contact 77 to the spark plug, from the side 93 of the line, conductors 92 and 91, contact segment 90, brushes 72 and 70, contact 77, and conductor 78. The brush 71 at the same time engages with the segmental contact 81, thereby establishing the circuit of the fuel supply motor from the side 93 of the line, by conductors 92 and 91 to contact segment 90, thence to brush 72, brush 71 and contact segment 81, thence by conductor 82 across the switch 44, it being remembered that the switch is maintained with the contact 84 in engagement with the contacts 83 and 85, the conductor 86 through the fuel supply motor 7 and by conductors 87 and to the opposite side of the line. The burner is thus supplied by the operation of the motor 7 with oil and at the same time is ignited. As soon as combustion commences in the combustion chamber heat is generated and passing up the stack afiects the combustion thermostat 16 so that by the time the switch arms 33 and 34 make a hall revolution the combustion thermostat will have been suficiently heated to move the switches 20 and 23 to the position with the switch '20 closed and the switch 23 open and the switch arm 33 will have moved to a position wherein the brush 72 has moved ofi the segment 90 and onto the segment 94, the brush 71, however, being still contacting with segment 81. Under these conditions the initial circuit for the motor 7 will be opened and a maintaining circuit established, from line 93, by conductors 92 and96 through the contacts of the switch 20, conductor to contact segment 94, and thence by brushes 72 and 71 to contact segment 81 and thence by conductors 82, switch 44 and conductor 86 to the motor 7, so that the motor will continue to run as long as combustion I, takes place in the combustion chamber of the furnace 2. By the time the switch member 33 has been moved to engage brush 72 with contact 94, the switch member 34 will have been moved to a position where brush 51 is out of contact with segment 57 and is in contact with the short contact segment. 61 and at the same time bnu'sh 50 will be in contactwith the segment 53; However, due to the fact that circuit through the contacts of the switch 23 has'been openerhdue to the tilting of this switch'member ina direction opposite to that illustrated in the drawing, the circuit through the control motor will be opened and the control motor brought to rest.

If for any reason the oil supplied to the burner 3 should have failed to ignite there would be no heat generated to cause the thermostat to operate, and the thermostat switches 23 and would remain in the position illustrated in Fig. 2 so that when the brush 72 engaged the contact segment 94 the circuit through the fuel supply motor would have been opened and the motor stopped, thus shutting oif the supply of oil. At the same time the control motor would have been stopped due to the opening of the stator circuit thereof by the passage of brush 72 off contact 90. Th'usfthe parts would be dormant in the oif position. Under. these conditions, in order to again start the apparatus, switch 44 must be operated to cause its con- 4 tact 97 to bridge its stationary contacts 98 and 99 respectively connected by conductors 100 and 101 with conductors 95 and 96. This re-establishes the stator circuit of the control motor from line 93, conductors 92, 96 and 101 across switch contact 97, conductors 100 and 95 to contact 94, brushes 72 and 69, contact 73, conductor 74, stator 47, and conductor 75 to line 7 6. -As'the rotor circuit of the control motor is already established from one brush of the motor through conductors 56 and across the contacts of the switch 23 to contact segment 53 and thence by brushes 50 and 52 to contact segment 66 and thence by conductor 67 to ground, the control motor will move the parts back to initial position whence the cycle of operation heretofore described will again commence. If upon repeated trials ignition does not take place the operator will of course know gone wrong with the apparatus and investigate. It is therefore apparent that upon the failure of initial ignition of the burner the oil supply pump can not operate sufficiently long to dangerously flood the combustion chamber.

Assuming that the furnace has been operated sufiiciently long'to raise the temperature in the room to the point where it is desired that no more heat should be supplied, under these circumstances, it being borne in mind that switch arm 33 is in position Where contact segment 94 is engaged by brush 72 and .switch arm 34 is in position where con'tact segment 61 is engaged by brush 51, when the thermostatic element 59 moves into engagement with the contact 65 the control motor circuit will be established from one brush of the rotor thereof by conductor 56, contact segments 57, conductor 58, thermostatic element 59 to contact 65 and thence byconduc- -tor 63 to contact segment 61, brushes 51 and 52, to contact segment 66' and thence by conductor 67 to ground. The control motor is that something has to the position shown in Fig. 2, that is, to

their cold position. When the switches 20 and 23, due to the cooling off of the combustion chamber, eventually reach their cold position, circuit is re-established for the control motor by the way of conductor 55 across the contacts of switch 23, conductor 54, contact segment 53, brushes 50 and 52 to contact segment 66 and thence by conductor 67 to ground. The control motor thus again starts up and moves the brush 51 off the dead contact 102 and ontothe contactisegment 57 so that it will continue to operate until it returns to normal or starting position with brush 51 resting on contact segment 60.

It will be noted that when the parts are in position with the brush 72 resting on contact 94 the circuit through the stator windings 47 of the control motor 46 is from line 93 by conductors 92 and 96, across the contacts in switch 20, by conductor 95 to contact segment 94 across switch arm 33 to brush 69 and thence to contact 73 and by conductor 74 throu h the stator windings 47 and back to line 76 by conductor 75. Therefore, if for any reason ignition fails in the combustion chamber of the furnace and as a result the combustion thermostat moves to cold osition, the position illustrated in Fig. 2, the circuit through the stator windings of the control motor will be opened and the motor .made inert against rotation irrespective of conditions in the motor circuit thereof, and in order to start the motor it will be necessary for the operator to close the circuit between contacts 98 and 99 of the switch 44 thereby re-establishing the stator winding circuit from line 93, conductors 92 and 101, conductor 97 across contacts 99 and 98, and thence by conductors 100 and 95 to contact segment 94 thence across switch member 33 to segment 73 and by conductor 74 through stator windings 47 and conductor 75 to line 76. This re-establishes the stator Winding circuit, and the motor will 0 crate to move the swltch members to their mitia] or starting positions.

The PIOVlSlOn of the circuit controlled by the switch-'23prevents the elimination of the stack thermostat as a controlling factor 1n the operation of the fuel supply motor. If for would continue to run after the stack temperature had dropped below the predetermined point, the presence of the switch 23 would render such unwarranted tampering ineffective as it is obvious that if for any reason the temperature in the stack falls-to such a point as to cause the stack thermostat to cool, circuit between the wires 54 and 55 will be closed by the operation of switch 23 so that with the thermostatic member 59 in con tact with the contact 94 the control motor would continually rotate starting and stop pin the fuel supply motor. With the switch 23 dlosed and the switch arm 34 moved to the position where the brush 50 engages contact 53 circuit would be established. through the rotor of the control motor by the way of-conductor 55, switch 23, conductor 54, contact 53, brush 50, brush 52 to contact 66 and thence by conductor 67 to ground and the motor would operate "to rotate the switch arm back to the position illustrated in Fig. 2. As the thermocontrol apparatus.

static arm 59-is in contact with the contact 64 the circuit through the rotor of the control motor would be by the way of conductor 56, contact 57, conductor 58, thermostat 59 contact 64 and conductor 62 to contact 60, brush 51, switch arm 34 to brush 52 and thence to contact 66 and by conductor 67 to ground, so that the motor would continue tooperate. It is therefore obvious that the control motor would thus continually rotate operating the fuel supply motor switch mechanism to intermittently close the circuit through this fuel supply motor and call attention to the fact that the apparatus is not in normal operating condition. If the switch 23 and its associated conductors 55 and 54 were entirely eliminated then when the switch arm moved to the position where brush 51 rests on contact 102 then the control motor would become dormant because its circuit would be perrnanently opened. It is essential that the switch 23 be closed before the switch arm can mahea complete movement from the point where the brush 51 rests on contact 61 to the point where thebrush 51 rests on contact 60.

The type of combustion thermostat having the friction drive connection between the thermostatic element and the switch member lends itself particularl for use in this type of T ere is a wide ran e of temperature change in the combustion chamber, on the other hand to produce the most satisfactory results the combustion control thermostat should operate in either direction in a very short range of the initial change in temperature. By the provision of the'friction drive the thermostatic device 0 erates during the wide range temperature 0 anges but is immediately effective to operate the switch upon a very slight change in temperature in the combustion chamber. A very slight rise in temperature'results from initial ignition and there is a long range above this,-

the thermostat movement takes place. Again on the return, in case of fire failure at a high temperature, it is again the early initial drop which is used to cut oil the fuel so that a large quantity of fuel may not be thrown into the hot combustion chamberto cause premature started by the closing of the manual switch the fuel supply motor circuit is opened preventing an additional discharge ofoil while the control motor is returning to its startingposltion.

In Fig. 3 I have shown, diagrammatically, a circuit connection for the control of the operation of the control motor, illustrating another method whereby the control motor circuit becomes a low voltage circuit, to avoid impressing high voltages on the thermostatic and other switch contacts controlling the operation of the control motor. In Fig. 2 l have illustrated a repulsion type of motor wherein for the purpose of starting and stopping the mjotor the short circuit across the brushes of the motor is controlled. in Fig. 3 I provide a means for controlling an alternating current motor used as a control motor wherein the circuit through the stator windings is controlled. As illustrated in Fig. 3 one terminal of the stator windings is connected with the line-76 by conductor The opposite terminal of the winding is connected by conductor 74 through the primary winding 103 oi? a transformer with the contact segment 73 of the oil burner motor control switch. This switch is similar to the switch illustrated in Fig. 2 and is provided with the switch arm 33 having the brushes 69, 70, 71 and 72 adapted to'contact respectively with the segments 73, 81, 77 and 90, the brush 72 being also adapted to contact with the short segment 94 as in Fig. 2. Likewise as in Fig. 2, the segment 90 is connected with conductor 91. The segment 94 is connected to conductor 95. The segment 81 is connected to conductor 82 and the segment 77 is connected to conductor 78 so that this switch I yet the initial slight rise is the range in which loll member will function in the same manner as heretofore described with respect to the structure illustrated in Fig. 2.

The secondary winding 104 of the transformer has one terminal connected to segment 57 of the control switch by conductor 56 and the other terminal connected to segment 66 by conductor 67 It is therefore apparent that the movement of the switch memer 34 will open or short-circuit the secondary winding 104 of the transformer in the same manner as in Fig.2 the switch member 34 opens the circuit through or short-circuits switching means, a control motor for operatthe brushes of the rotor 48 of the control motor. When the circuit through the second ary winding 104 is open there will be developed in the primary winding 103 of the transformer sufficient back E. M. F. to prevent the flow of any current through the stator windings of the control motor and the control motor will therefore not operate. As soon, however, as the windings 104 are shortcircuited in a manner similar to that described in short-circuiting the brushes of the rotor 48 the back E. M, F. through the rimary windings 103 will become negligi le admitting sufficient current to the stator windings of the control motor and permitting the same to operate.

While I have shown and described an oil pump 5.0perated by an electric motor 7 for controlling the supply of oil to the burner 3 it will be obvious that other electro-magnetically operated devices may be substituted for the pump without departing from the spirit of the. invention, and where I have used in the claims the expressions fuel motor and control motor it will be understood that f contemplate the use of any electro-magnetic means for controlling the fuel supply and any electro-magnet-ic means for operating the control switches.

In some of the claims burner motor refers to the motor 7 control motor refers to the motor portion of the element 8; safety switch refers to the switch 20 responsive to normal burner conditions.

I claim as my invention:

1. The combination with an oil burner having a fuel supply, of a fuel motor formember having a circuit under the control of said fuel-motor switch and said thermostatically-controlled switching means.

2. The combination with an oil burner having a fuel supply, of a fuel motor for controlling said fuel supply and having an initial starting circuit and a maintaining circuit, a switch controlling each of said circuits, 'a thermostatic element directly subject to combustion conditions and having switching means controlling said maintaining circuit, the movable member of said fuel motor switch being adapted to-open the maintaining circuit and close the initial starting circuit independently of the thermostatically-controlled having a fuel supply, of a fuel motor for controlling said fuel supply, a switch for con trolling the operation of said fuel motor, a control motor for operating said switch, a second switch for controlling the operation of said control motor, a thermostatically operated switching means co-operating with both of said switches for controlling the op 35 eration of said control motor, and a thermostatic elemcnt directly subject to combustion conditions for actuating said last mentioned switching means.

4. The combination with an oil burner having a fuel supply, of a fuel motor for controlling said fuel supply, a control switch for said motor, a thermostatic element directly subject to combustion conditions, switching means controlled by said thermostatic element and co-operating with said control switch for controlling the operation of said fuel motor, a control motor for operating said control switch, a switch for controlling the operation thereof, said thermostatically 0011- trolled switching means being arranged to cooperate with both of said control switches for controlling the operation of said control motor.

5. The combination with an oil burner having a fuel supply, of a fuel motor for controlling said fuel supply, a control switch for controlling the operation of said fuel motor,

a control motor for operating said control switch, a second control switch for said 0 control motor, thermostatically controlled switching means co-operating'with said first control means for controlling the operation of said fuel motor and co-operating with said second control switch for controlling the operation of said control motor, and a thermostatic element directly subject to combustion conditions for actuating said thermostatically-controlled switching means.

6. The combination with anoil burner hav- 12o ing a fuel sup ly, of a fuel motor for controlling said he supply, a control switch for said motor,a control'motor for operatin said control switch, a control switch for sai control motor, a thermostatically operated switch .co-opera'ting with said second control switch,

ject to combustion conditions for operating said thermostatically controlled switches.

7. The combination with an oil burner having a fuel supply, a fuel motor for controlling said fuel supply, a control switch havin a starting circuit and a maintaining circu1t for'said fuel motor, a control motor for said control switch, a second control switch driven by and controlling the operation of said control motor, a thermostatic element and switching means, operated by said thermostatic element, which when moved from one position to another co-operates with said first mentioned control switch for establishing said maintaining circuit and co-operates with said second mentioned control switch for stopping said control motor when the first control switch has been moved to maintaining circuit position.

8. The combination with an oil burner having a fuel sup ly, a fuel motor-for controlling said fuel supp y, a control switch for said-motor, 'means havin ing said control switch, a second control "switch driven by and controlling said control motor, a thermostatic element directly subject to combustion conditions'and switching means, 0 erated by said thermostatic element, which w en movedfrom initial to maintaining position co-operates with said first mentioned control switch to close said maintaining circuit and with said second mentioned control switch to stop said control motor with the first mentioned control switch in' maintaining position and when moved to'initial position opens said maintaintng circuit trolling apparatus, the combination of a control motor, thermostatically-controlled switching means therefor, a fuel supply motor, switching means mechanicallyiconnected g 10. In an electrically operated burner conto said thermostatically-controlled means trolling apparatus, the combination of a control motor, thermostaticallycontrolled switching means therefor, a fuel supply motor, switching means mechanically connected to said thermostatically-controlled means and adapted to operate synchronously therewith, a thermostat responsive to combustion conditions and controlling two switches, one

switch to maintain the fuel supply motor circuit, the other switch to establish the control motor circuit, and a manually-controlled member to open the fuel supply motor circuit and close the stator circuit of the control 'motor. a starting circuit and a t maintaining circu1t, a control motor for driv- 12. The combination'with an oil burner,of a fuel motor co-operating therewith, a switch for controlling the operation of said fuel motor, a control motor for operating said switch, a second switch for controlling the operation of said control motor, a thermostat responsive to combustion conditions, a mercury switch operated by said thermostat and adapted to maintain the fuel supply motor circuit, and a second mercury switch operated by said the ostat and adapted to close the rotor circuit f the control motor in v the absence of combustion. u

13. The combination with an oil burner, of a fuel motor co-ope'rating therewith, a switch for controlling the operation of said fuel motor, acontrol motor, for operating said switch, a second switch for controllmg the operation of said control motor, a thermostat responsive to combustion conditions, a mercury switch operated bysaid thermostat and adapted to maintainvt e fuel supply motor circuit, and a second mercury switc operated by said thermostat and adapted to open the rotor circuit of the control motor during normal operation of the fuelsupply motor. In witness whereof, I, PAUL Smvms, have hereunto set my hand at Wabash, Indiana, this 6th day of November, A. D. one thousand nine hundred and twenty-five.

PAUL F. SHIVERSI 

